This invention relates to control shafts to which control elements are affixed and to a method for manufacturing such control shafts.
German Offenlegungsschrift No. 37 17 190 discloses a camshaft for controlling valves in internal combustion engines in which the camshaft consists of a cylindrical shaft member onto which control elements in the form of cams are pushed so as to be connected rigidly to the shaft. In that case the cams are designed as one-piece sintered parts having an aperture which is provided with radial projections to receive the shaft. The shaft is formed with regions having a slightly larger diameter in certain areas, the axial extent of those regions corresponding to the width of the control cams. As the cams are pushed onto the regions of enlarged diameter, the radial projections in the aperture cut grooves along the enlarged region and the material displaced from the grooves is evidently lost. An extremely torsionally rigid connection is formed in this way between the cams and the shaft member.
That document also discloses a method for the manufacture of the above-mentioned camshaft in which a first enlarged shaft region is formed and, after a first cam has been mounted on that region, further regions of enlarged diameter are formed in succession and, after each enlarged diameter region is formed, another cam is pushed onto that region.
German Offenlegungsschrift No. 44 23 107 discloses the manufacture of cams, such as those for controlling the intake and exhaust valves of an internal combustion engine, from a multiplicity of layers of flat stock. For this purpose, a number of layers of stock are punched out of a steel sheet, for example a cold-rolled steel sheet, and then mounted together to form a cam assembly. In the punching operation, an aperture is formed in each layer to receive a shaft member when assembled and, at a distance from the resulting shaft aperture and parallel with the shaft axis, the cam assembly has an opening with a diameter which is significantly smaller than that of the shaft aperture. A pin formed with a collar and having a length which is greater than the width of the cam assembly is then inserted through smaller opening in the assembly. A washer is mounted on the projecting end of the pin and is welded to the pin on the side facing away from the cam. This arrangement of a pin and a washer-prevents the sheet assembly from falling apart but it does not prevent relative displacement between the adjacent layers of flat sheet stock about the longitudinal center line of the pin. This requires separate laser welds along two opposed grooves in the shaft aperture.